Questions tagged [power-supply]

An electronic device which supplies electrical energy to a load. Can be AC or DC input. Typically DC output.

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Arduino Uno R3: Directly supply regulated 5V to 5V pin?

I'd like to use an Arduino Uno R3 battery powered a datalogger. I want do supply it directly with a Step-Up regulated 5V rechargable battery powersource at power ...
22
votes
3answers
25k views

How do the tiny AC->USB power supplies work?

The iPhone and Kindle both come with tiny power supplies that take in 120v AC and output around 5V at 0.85 to 1 amp. They seem to be too small and light to have a transformer, and generate very little ...
6
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5answers
65k views

How to get high current from 9 volt batteries

I am planning to make a solenoid.. Which should be so powerful as to lift up about 600N force. I have thought about it, and I have a doubt. How can I get DC currents up to 20-30 A using a 9 V battery? ...
18
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4answers
37k views

Why is it bad to mix new and old batteries?

I've seen warnings that it's bad to mix new and old batteries -- why? Is it a matter of a battery's age or a battery's voltage/current (remaining)?
14
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7answers
9k views

How can a faulty USB charger kill you?

This question relates to this incident here, where a women in Australia died from a faulty USB charger that allowed the full 240V mains voltage through the USB cable. Now from my understanding you ...
11
votes
1answer
3k views

Measuring ferrite core parameters

I have large amounts of inductors and transformers from power supplies or other undocumented sources. They are of course completely unmarked and I have no idea what kind of ferrite material they are ...
22
votes
3answers
19k views

Should I isolate grounds of an isolated DC/DC converter?

If I use an isolated DC/DC converter, when designing the PCB, should I isolate the ground of the input and the ground of the output as shown below? I've never isolated grounds (except for AGND and ...
16
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5answers
75k views

Powering laptop from 12V sources without inverter

This question has two parts: 1) How inefficient is it to boost 12V to 120V and then back to 12V as in using a traditional car power inverter to power a laptop (i.e. the 12V car battery power is ...
18
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10answers
9k views

Is there a constant power supply?

A voltage source is a device that produces constant voltage, but allows amperage and power to vary, in accordance with the laws of electricity. A current source is a device that produces constant ...
13
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6answers
53k views

Is it possible to power a cordless drill from wall socket adapter?

I have a dewalt 18V cordless drill. I am wondering if it is feasible to build an adapter that can power the drill from a standard US wall socket? A typical DeWalt drill needs 2.6 amps with no-load. I ...
8
votes
2answers
5k views

Ripple current in a linear power supply transformer

I'm a bit confused regarding linear supplies and their input currents (i.e. on the input side of the voltage regulator). To start with, here's a test circuit: \$R_{bogus}\$ is just to make LTspice ...
20
votes
5answers
2k views

Why is it so problematic to have close to zero standby power consumption?

Each electronic device consumes electric power when it is "idle" unless it has a mechanical switch. I can understand that for example a TV with a remote control needs to "be ready" to receive a ...
13
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2answers
1k views

Getting rid of AC/DC adapters

Many of us have lots of devices that uses AC mains (110V/220V) to DC (typically 12VDC, 9VDC and sometimes 15VDC) adapters. There's my Wi-Fi router, my powered speakers, printer, scanner, etc. So I ...
10
votes
2answers
3k views

LED accent light that slowly dims when removed from power source

We've all played with different transformers and power supplies that have an LED indicator that dims before going out entirely when the power supply is unplugged. I'm working on designing an accent ...
8
votes
4answers
3k views

3 Contact Laptop Power Supply

So I'm wondering if anyone has any information about the Dell power supplies which have 3 contacts on the barrel. I know the 3 are power, ground, and some sort of communication link. Does anyone know ...
7
votes
3answers
17k views

Using PWR_OK to Activate an ATX Power Supply Automatically

Okay so, I have an ATX PSU that isn't connected to a motherboard, and I'm currently using the simple paper-clip trick to ground PS_On in order to trick the PSU into ...
3
votes
4answers
10k views

Charging 3 AAs in series

I'm currently repairing a project built by someone else and want to avoid tinkering with it as much as possible. I am looking to recharge 3 AA NiMH batteries (at 1.2v each), that are in series. I ...
3
votes
0answers
116 views

How can i transfer 12 V, 50 Hz, 1 A wirelessly? [closed]

I want to transfer electical power wirelessly from a transmitter to a receiver coil. Input energy is provided by a single phase step-down transformer - 230V/12V AC, 50 Hz, 1,000 mA. Using the 12 V ...
8
votes
1answer
3k views

Battery in parallel with main power source

I have a system that is powered by a main voltage supply and I want to connect it to a battery for backup, in case of power outage. I need to know what would happen if I connect the system with the ...
7
votes
4answers
6k views

Why a neon lamp indicator on power strip switch flickers in the dark?

Neon lamp indicators embedded in power strip switches indicate whether the switch is ON or OFF. When the neon lamp is ON in a dark environment (lights of the room are off) the lamp start to ...
5
votes
2answers
7k views

Calculating the True Power Factor in non-linear loads

In my circuit I am taking in 60 Hz 120 VAC from the power company and hooking it up to a AC/DC non-linear switching buck converter I am designing. I know that: true power factor = (displacement power ...
5
votes
5answers
31k views

Why do electronic circuits need their power supply to be DC, or rectified AC?

I'm pretty sure the answer to this should be obvious - even to me ... It's been a while I've been reading and attempting to construct simple electronic circuits. The supply almost always is either ...
3
votes
3answers
2k views

Designing ammeter for an external ATX power supply adapter

I'm trying to design and build an external ATX power supply adapter, much like this one. I want to use it as a benchtop power supply. I wanted my adapter to have one more feature: I wanted it to have ...
3
votes
2answers
7k views

What's a simpler way to switch between power sources?

I want to make a device that allows the user to switch between two different power sources (a wall mount and batteries). I could perform this circuit using two DPDT switches, but I would need to ...
2
votes
1answer
4k views

Putting two wall-warts in series?

I'm helping a friend make a 48 inch hot-wire foam cutter. He would like it to be as economical as possible, so I'm giving him two 15V 1.1A wall wart power supplies that I have sitting around. I don't ...
2
votes
3answers
926 views

Paralleling power supplies for higher current

I am looking at using two Cincon (CFM80S240 and CFM60S240) power supplies in parallel to achieve a higher current output. Is this possible? If so, can I just hook them up in parallel, or is there some ...
4
votes
3answers
3k views

Creating a small scale bumper car ground power grid

I'd like to build a tiny RC car that can run indefinitely without the need to charge. Bumper cars have strips of power on the ground and according to Wikipedia this is how they work: "Uses ...
1
vote
3answers
1k views

Why do LEDs require a constant current source and not a constant voltage source as power supplies?

Most electronic devices use constant voltage source as power supplies. Why do LEDs require constant current source?
1
vote
1answer
159 views

Is there a good topology for splitting a DC power supply from a few LM2576 and LM2577?

So, this isn't the most serious project, more of a toy/hack, but I have a some LM2576 and LM2577 and I wanted to see if I could somehow get an adjustable dual rail (bipolar) supply out of them, for ...
1
vote
2answers
172 views

Power supply noise problem in a measurement system

This might be a bit long to explain but actually a power supply noise is affecting a system's measurements. I will briefly try to explain the system and the noise issue with several pics. This is ...
61
votes
11answers
299k views

How can I tell the size of a barrel power connector?

Spring cleaning, and I'm trying to get power supplies for all my devices with missing power supplies. They're all the typical barrel power connector, and I'm having a dickens of a time trying to ...
20
votes
7answers
60k views

When people talk about a device “drawing” current, what do they mean? Why do devices under load “draw” more current?

In my (extremely rudimentary) understanding, the amount of current flowing in a circuit is determined by a) its resistance, and b) the voltage of the power source (voltage from beginning to end), ...
33
votes
6answers
35k views

Can an audio circuit be powered by a switched-mode power supply?

Most audio circuits a powered with large, heavy transformers and a small ripple after smoothing. SMPS are smaller and more efficient. EMI can be shielded by a metal enclosure and the output filtered ...
17
votes
2answers
30k views

Constant current, constant power and constant impedance loads

Ive been looking for information on constant power, constant current and constant impedance/resistance loads, there's some information about the constant current loads, but very little that really ...
9
votes
7answers
91k views

Voltage at what Amperage

I've often seen devices with power requirements specified only in Volts (e.g. 7-12V) but never the amperage. I've wanted to run various embedded devices of wall warts and batteries (the devices have ...
10
votes
6answers
18k views

Automatically switching from 9V battery to DC wall adapter on insertion

I have a simple circuit that runs off of a 9V battery. I'm re-designing it so that it can also run off of an external 12V DC source (ie: a wall adapter). I want to design the circuit so that if both ...
38
votes
1answer
2k views

What is / how can I get a student-safe power supply for electronics projects?

What is / how can I get a student-safe power supply for electronics projects? I'm looking for a student-safe power supply for solder less breadboard. I'm developing a course to teach electrical ...
9
votes
7answers
80k views

Why does the USA use 110V and UK use 230-240V?

Why does the USA use 110V and UK use 230-240V? What are the advantages? Explain me with calculation. Why do they use different frequencies like 50Hz, 60Hz? What is the reason?
22
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4answers
20k views

What is the usage of the negative voltages on a PC motherboard?

What is the usage of theses negative voltages? Are they there only for backward compatibility? In nowadays PC power supplies, we have: +12V +5V +3.3V but also: -12V -5V But the current rating of ...
12
votes
5answers
2k views

What are some alternative power sources for wireless sensors?

I'm looking to power several small, Wi-Fi enabled sensors, in a domestic home or office environment. As such I'm interested in keeping them powered as long as possible between charges. Obviously an ...
8
votes
1answer
7k views

NMOS FET selection for reverse polarity protection

I am working on a reverse polarity protection circuit, similar to that in Figure 2 of SLVA139: Reverse Current/Battery Protection Circuits. Here is my circuit: My case is slightly more complex due to ...
8
votes
3answers
11k views

Help needed optimising simple current limiting circuit

I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I have started using a circuit like the one found on this ...
6
votes
2answers
9k views

Arduino backup power supply

As a complete beginner in the field of electrical engineering, I am trying to build an alarm system on an Arduino board. I want to power my board using an external 10V power supply. In case of power ...
14
votes
6answers
20k views

To what extent are “pure sine wave” power supplies marketing spin?

Recently, I've noticed a trend in power supply manufacturers touting their PSUs (generator or battery inverter etc.) as having a pure sine wave output. I've also seen people saying that warranties ...
14
votes
6answers
20k views

My MOSFET operated solenoid circuit destroys my Arduino inputs

I made a series of PCBs to power some solenoid valves that use an external power supply. I switch them with BS170 MOSFETs using an Arduino as gate signal. I based it a solution by Jason S. This is an ...
12
votes
2answers
1k views

Does switched-mode power supply feature galvanic separation?

I've carefully read Wikipedia article and can't get one important thing - is there galvanic separation in such supply? The diagram in that article goes like this: ...
12
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3answers
1k views

Why is the PCB so large on this SMPS?

In a post regarding heat dissipation in a linear regulator, one answer provided this nice little pin-equivalent smps. It was a great reply, and I'll likely order a few myself. I am wondering though, ...
12
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2answers
8k views

Power Supply Design - Multiple Voltage Regulators

I'm trying design a benchtop DC power supply for powering small projects, breadboards, arduino, etc. This is a list of what I want from it: Fixed voltage rails for 24V, 12V, 9V, 5V & 3.3V Edit: ...
11
votes
2answers
5k views

Soldering a high-power cable to a PCB

I want to make a power connection between my PCB and an accumulator. I need it to handle up to 100A, and to be mechanically very strong, because it will be on board of a buggy car model. In the ...
8
votes
6answers
3k views

Why Did My NPN/PNP Voltage Regulator Experiment Explode?

I have been looking at ways to derive low voltage rails from a higher voltage and current supply, which in practical terms is about 53-0-53V from a linear power supply (toroidal, bridge rectifier and ...